/**
 * jTweener.easingFunctions is Tweener's easing functions 
 * (Penner's Easing Equations) porting to JavaScript.
 * http://code.google.com/p/tweener/
 * @author Robert Penner
 */

jTweener.easingFunctions = {
	easeNone: function(t, b, c, d) {
		return c*t/d + b;
	},
	easeInQuad: function(t, b, c, d) {
		return c*(t/=d)*t + b;
	},
	easeOutQuad: function(t, b, c, d) {
		return -c *(t/=d)*(t-2) + b;
	},
	easeInOutQuad: function(t, b, c, d) {
		if((t/=d/2) < 1) return c/2*t*t + b;
		return -c/2 *((--t)*(t-2) - 1) + b;
	},
	easeInCubic: function(t, b, c, d) {
		return c*(t/=d)*t*t + b;
	},
	easeOutCubic: function(t, b, c, d) {
		return c*((t=t/d-1)*t*t + 1) + b;
	},
	easeInOutCubic: function(t, b, c, d) {
		if((t/=d/2) < 1) return c/2*t*t*t + b;
		return c/2*((t-=2)*t*t + 2) + b;
	},
	
	easeInExpo: function(t, b, c, d) {
		return(t==0) ? b : c * Math.pow(2, 10 *(t/d - 1)) + b - c * 0.001;
	},
	easeOutExpo: function(t, b, c, d) {
		return(t==d) ? b+c : c * 1.001 *(-Math.pow(2, -10 * t/d) + 1) + b;
	},
	easeInOutExpo: function(t, b, c, d) {
		if(t==0) return b;
		if(t==d) return b+c;
		if((t/=d/2) < 1) return c/2 * Math.pow(2, 10 *(t - 1)) + b - c * 0.0005;
		return c/2 * 1.0005 *(-Math.pow(2, -10 * --t) + 2) + b;
	},
	
	easeInElastic: function(t, b, c, d, a, p) {
		var s;
		if(t==0) return b;  if((t/=d)==1) return b+c;  if(!p) p=d*.3;
		if(!a || a < Math.abs(c)) { a=c; s=p/4; } else s = p/(2*Math.PI) * Math.asin(c/a);
		return -(a*Math.pow(2,10*(t-=1)) * Math.sin((t*d-s)*(2*Math.PI)/p )) + b;
	},
	easeOutElastic: function(t, b, c, d, a, p) {
		var s;
		if(t==0) return b;  if((t/=d)==1) return b+c;  if(!p) p=d*.3;
		if(!a || a < Math.abs(c)) { a=c; s=p/4; } else s = p/(2*Math.PI) * Math.asin(c/a);
		return(a*Math.pow(2,-10*t) * Math.sin((t*d-s)*(2*Math.PI)/p ) + c + b);
	},
	easeInOutElastic: function(t, b, c, d, a, p) {
		var s;
		if(t==0) return b;  if((t/=d/2)==2) return b+c;  if(!p) p=d*(.3*1.5);
		if(!a || a < Math.abs(c)) { a=c; s=p/4; }       else s = p/(2*Math.PI) * Math.asin(c/a);
		if(t < 1) return -.5*(a*Math.pow(2,10*(t-=1)) * Math.sin((t*d-s)*(2*Math.PI)/p )) + b;
		return a*Math.pow(2,-10*(t-=1)) * Math.sin((t*d-s)*(2*Math.PI)/p )*.5 + c + b;
	},
	easeInBack: function(t, b, c, d, s) {
		if(s == undefined) s = 1.70158;
		return c*(t/=d)*t*((s+1)*t - s) + b;
	},
	easeOutBack: function(t, b, c, d, s) {
		if(s == undefined) s = 1.70158;
		return c*((t=t/d-1)*t*((s+1)*t + s) + 1) + b;
	},
	easeInOutBack: function(t, b, c, d, s) {
		if(s == undefined) s = 1.70158;
		if((t/=d/2) < 1) return c/2*(t*t*(((s*=(1.525))+1)*t - s)) + b;
		return c/2*((t-=2)*t*(((s*=(1.525))+1)*t + s) + 2) + b;
	},
	easeInBounce: function(t, b, c, d) {
		return c - jTweener.easingFunctions.easeOutBounce(d-t, 0, c, d) + b;
	},
	easeOutBounce: function(t, b, c, d) {
		if((t/=d) <(1/2.75)) {
			return c*(7.5625*t*t) + b;
		} else if(t <(2/2.75)) {
			return c*(7.5625*(t-=(1.5/2.75))*t + .75) + b;
		} else if(t <(2.5/2.75)) {
			return c*(7.5625*(t-=(2.25/2.75))*t + .9375) + b;
		} else {
			return c*(7.5625*(t-=(2.625/2.75))*t + .984375) + b;
		}
	},
	easeInOutBounce: function(t, b, c, d) {
		if(t < d/2) return jTweener.easingFunctions.easeInBounce(t*2, 0, c, d) * .5 + b;
		else return jTweener.easingFunctions.easeOutBounce(t*2-d, 0, c, d) * .5 + c*.5 + b;
	}
};
jTweener.easingFunctions.linear = jTweener.easingFunctions.easeNone;
